Seal member, assembly and method

ABSTRACT

A brush seal assembly and method for a turbine machine having a rotary member and a stationary member circumscribing the rotary member. The seal assembly is comprised of a sealing member disposed at a radially inward region of the stationary member and a portion of the sealing member is in rubbing contact with the contact region. The sealing member is detachable from the stationary member for selective replacement and incorporates at least one integrally formed seal element.

BACKGROUND OF THE INVENTION

The present invention generally relates to dynamic seals of the typeused in turbo machinery.

Labyrinth-type packings and brush seals are widely used in steamturbines and in aircraft and industrial gas turbines to provide dynamicseals between the rotating and static turbine components, such as therotor and diaphragm inner web of a steam turbine. Traditional labyrinthpacking comprises a series of (hard) teeth that project radially inwardfrom the circumference of a static component and toward but out ofcontact with the rotary component, thereby defining a series of partialbarriers that create a tortuous axial flow path immediately adjacent thesurface of the rotary component.

Brush seals typically comprise metal bristles that, similar to the teethof a labyrinth packing, project radially inward from the circumferenceof a static component toward a rotary component. In contrast tolabyrinth packings, brush seals are normally intended to be in rubbingcontact with the adjacent circumferential surface of the rotarycomponent, creating a substantially continuous barrier to flow aroundthe circumference of the rotary component. In this regard, brush sealsprovide a more effective barrier to secondary flow losses, i.e., providebetter sealing performance, as compared to labyrinth packings, andtherefore have the potential for significantly improving performance.

The rotors of aircraft and industrial gas turbines are relatively stiff,and as a result their dynamic behavior is not generally affected byrubbing contact with a brush seal. In contrast, the rotor of a steamturbine typically includes a continuous solid shaft to which buckets areattached. Impulse-type steam turbines typically operate above therotor's first bending critical frequency, and often near the secondbending critical frequency. It has been shown that the rubbing contactbetween a brush seal and the rotor of a steam turbine can magnify rotorvibration through the first and second critical speeds of a rotor,resulting in unacceptable radial rotor movement. It is believed thatthis effect is particularly likely to occur if the rotor is bowed as aresult of thermal, dynamic or manufacturing circumstances. Moreparticularly, the friction resulting from the rubbing contact locallyincreases the surface temperature of the rotor, leading to nonuniformsurface temperatures along its circumference. Because high (proud) spotsof a bowed rotor are particularly prone to heating in this manner frommore intense rubbing contact, the localized heating caused by brushseals can further increase bowing in a rotor as a result of nonuniformthermal expansion about the rotor circumference, thereby exacerbatingvibration and rotor dynamics concerns.

In commonly assigned U.S. Pat. No. 6,821,086, the disclosure of which isincorporated herein by this reference, a seal assembly and methodtherefor are disclosed that are capable of significantly reducingvibration and rotor dynamics concerns that arise in turbo machinery,such as steam turbines, as a result of localized heating caused by sealsin rubbing contact with a rotary member of the turbo machine.

The configuration of the '086 patent is acceptable when multiple hardteeth are needed and when there is sufficient room for a large dovetailhard tooth carrier. For cases where fewer hard teeth are needed andthere is little room, however, the large hard tooth carrier and brushseal carrier configuration of the '086 patent may not work. A smallerdesign would therefore be desirable. As depicted in FIG. 2 some hardteeth are actually machined to the nozzle structure. However, if such aseal structure is worn through rubbing, the hard tooth seal structurecannot be replaced.

BRIEF DESCRIPTION OF THE INVENTION

As noted above, current brush seal carriers take up significant room,driving up the amount of material needed to hold the carriers in placeand restricting where the seals can be installed. As also noted above,some hard teeth are actually machined to the nozzle assembly so if theseal is worn, it cannot be replaced.

The invention proposes to reduce the amount of material necessary forforming a seal assembly while allowing all sealing devices to bereplaced if necessary without any manufacturing or modification to thenozzle.

In an example embodiment of the invention, a brush seal carrier isprovided that reduces the footprint of the brush seal assembly and itscarrier while also integrating a hard tooth seal as asecondary/redundant/backup seal into the carrier. Integrating the hardtooth seal into the carrier provides for ease of replacement while thesmall footprint allows the brush seal to be installed in smaller areas.Integrating the hard tooth structure allows the hard tooth to beprovided with minimal support structure and yet allows the hard tooth tobe replaced in the event it becomes worn.

Thus, the invention may be embodied in a seal member for a turbo machinecomprising: a brush seal carrier; a brush seal component mounted to saidbrush seal carrier so that a portion of said brush component projectsfrom said brush seal carrier, and at least one hard tooth seal elementintegrally formed with said brush seal carrier so as to extend ingenerally parallel relation to at least a part of said portion of saidbrush component that projects from said brush seal carrier.

The invention may also be embodied in a seal assembly for a turbomachine having a rotary assembly rotatable about an axis and astationary assembly encircling the rotary assembly, the rotary assemblydefining outer peripheral surfaces and the stationary assembly having aportion radially facing the rotary assembly so as to be in opposedfacing relation to an outer peripheral surface thereof, the sealassembly comprising at least a portion of said outer peripheral surfaceof the rotary assembly and a plurality of seal elements provided on aseal carrier on said radially facing portion of the stationary assembly,said plurality of sealing elements including at least one seal elementmounted to said seal carrier and disposed in rubbing contact with saidouter peripheral surface and at least one hard tooth seal element thatis spaced from said outer peripheral surface, and wherein said hardtooth seal element is defined integrally in one piece with said sealcarrier.

The invention may further be embodied in a method of providing a seal ina turbo machine, between a rotary member rotatable about an axis and astationary member encircling the rotary member, the rotary member havingan outer circumferential surface; comprising: providing a seal assemblyincluding first and second seal components at a radially inward regionof the stationary member, the first seal component having a portionthereof in rubbing contact with the outer circumferential surface of therotor and the second seal component being integrally formed in one piecewith a carrier of said first seal component and extending in generallyparallel relation to the first seal component but spaced from said outercircumferential surface.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of this invention, will be morecompletely understood and appreciated by careful study of the followingmore detailed description of the presently preferred exemplaryembodiments of the invention taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 represents a fragmentary longitudinal cross-sectional view of adiaphragm packing area of a steam turbine equipped with a sealingassembly of a related art;

FIG. 2 is a schematic representation of another sealing assembly of arelated art;

FIG. 3 is a schematic representation of a sealing assembly according toan example embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a diaphragm packing area of a steam turbineequipped with a sealing assembly in accordance with '086 patent isillustrated. The steam turbine has a rotor 10 on which axially spacedwheels 12 are formed or mounted and to which buckets 14 are attached.The rotor 10, wheels 12, and buckets 14 rotate about the rotor axis and,therefore form part of a rotary portion of the turbine. A diaphragm(nozzle) inner ring (web) 16 extends radially inwardly between wheels12, defining separate stages of the turbine. A casing 18 surrounds rotor10 and with nozzle inner ring 16 supports a nozzle partition 20. Thering 16, partition 20 and casing 18 together form part of a stationaryportion of the turbine, disposed in a plane normal to the rotor axis andsurrounding an outer circumferential region of the rotor 10. Steam flowsthrough the bucket 14 and nozzle partition 20.

The turbine depicted in FIG. 1 is equipped with Labyrinth packings 22,24 and 26. Labyrinth packings 22 and 24 are mounted to a packing ringsegment or a hard tooth carrier 28 and Labyrinth packing 26 is mountedto a packing ring segment 30. As is conventional, each packing ringsegment 28, 30 is one of multiple arcuate segments that are assembledcircumferentially to the nozzle inner ring 16 or casing 18,respectively. The Labyrinth packings 22, 24 and 26 reduce secondary flowlosses between the rotary and stationary components, more particularly,between the rotor 10 and nozzle inner ring 16 and between the buckets 14and casing 18. While effective, it is understood that the Labyrinthpackings 22, 24 and 26 cannot reduce secondary flow losses to the extentpossible with brush seals because of the gap between the hard teeth 32,33 of the respective Labyrinth packings and the opposing surfaces withwhich they seal. Thus, in accordance with the '086 patent, the packingring segment or hard tooth carrier 28 mounted to the nozzle inner ring16 further includes a brush seal 34 situated axially between the sets ofLabyrinth packings 22 and 24. The Labyrinth packings 22 and 24 thusserve as a backup seals to the brush seal 34. In contrast to packings 22and 24, brush seal 34 is adapted to continuously contact the surfacewith which it is intended to seal, thereby effecting a better seal thanpossible with the Labyrinth packings 22 and 24. As is conventional,brush seal 34 is equipped with bristles 36 and, as mentioned above,Labyrinth packings 22 and 24 are equipped with hard teeth 32 thatproject radially towards rotor 10.

As understood, the rubbing contact that occurs between brush seal 34 androtor 10 inherently causes frictional heating. In the '086 patent,better distribution and dissipation of the heat are achieved byincluding a raised section 38 on the rotor which projects radiallyoutward beyond axially adjacent surface regions 40 to define a platform42. The raised section 38 defines a cavity 44 that is completelyenclosed so that it contains, e.g., only air that was trapped duringformation thereof.

FIG. 3 represents the same turbine illustrated in FIG. 1 but wherein theseal assembly has been modified according to an example embodiment ofthe invention so as to reduce the footprint of the brush seal carrier146 while also integrating a hard tooth seal 122 to serve as a backupseal to the brush seal. Referring more specifically to the exampleembodiment of the invention schematically depicted in FIG. 3, the brushseal assembly 146 is comprised of a compliant bristle 136 extendingradially towards the rotor and providing a tight seal with the facingsurface of the rotating shaft (not shown). Although not illustrated indetail in FIG. 3, in an example embodiment, the rotor structure inopposed relation to the brush seal may include a platform structure 42of the type depicted in FIG. 1 and disclosed with reference thereto, toeffectively distribute and dissipate heat generated by the rubbingcontact of the brush seal and the rotary member as it rotates about itsaxis.

In the illustrated embodiment, rather than providing a dovetail forreceipt in a dovetail groove, the carrier 146 has a single engaging hookor flange 148. The carrier 146 is illustrated as received in a shapedgroove 150 in the diaphragm inner ring (nozzle web) 116 so that the hook148 is received in channel 152. In the illustrated example, moreover,the brush seal carrier 146 is a laminated structure comprised of thecompliant bristle 136 sandwiched between front and back plates orcarrier parts 154, 156. The front carrier part 154 includes a spacerportion 158 to space the compliant bristle 136 from the balance of thefront plate, to allow forward axial flexing in a conventional manner.The back plate 156, on the other hand, includes a projecting support 160to limit aft flexing of the compliant bristle 136.

In an example embodiment of the invention, at least one hard tooth sealelement 131 is incorporated in the brush seal carrier 146 to extendradially in parallel to, but to a lesser extent than the bristles 136 tothus provide a backup seal to the bristles 136. To reduce the footprintof the brush seal carrier 146, rather than providing a separate hardtooth element 32 as in the FIG. 1 structure, an integrated hard tooth131 is provided. Thus, the carrier part (154 in the illustratedembodiment) is machined out of metal and includes a hard tooth 131integrally machined into it. The brush structure 136 is laminated withand welded into the carriers 154, 156 to provide the rotary part of theseal assembly 146. The remaining parts of the turbine structuregenerally correspond to those as depicted by way of example in FIG. 1and therefore are not illustrated again in FIG. 3, even through it is tobe understood that those corresponding parts are advantageously providedin this example embodiment.

As will be understood, hard tooth integration facilitates a reduction inthe dimension of the seal carrier while allowing the hard tooth to bereplaced if it is rubbed out. This also allows for a reduction in theamount of parts required for assembly. As described above, the FIG. 1configuration included a large brush seal carrier 34 that is installedinto a hard tooth carrier 28 for multiple hard teeth. This adds to thematerial and space requirements for the assembly. It also dictates usingmore hard teeth 32 than may be necessary because of the sealing efficacyof the brush seal. The integrated configuration proposed hereinabove andschematically depicted in FIG. 3 allows the carrier 146 to be designedto have as few as one hard tooth 131. Furthermore, as will beappreciated, configuring the brush seal carrier 146 as a laminatedassembly of plates and bristles that is mounted directly to, e.g., thenozzle web 116 further substantially reduces the axial dimension of theseal assembly 146 as compared to e.g. the seal carrier 28 depicted inFIG. 1.

It is to be understood that while example carrier part 154, 156configurations have been illustrated and described, the carrier partsmay have configurations and shape particulars that are different fromthe illustrated example. For example, although the back plate has beenillustrated as including a hook for engaging the channel 152 of thegroove 150 in the nozzle web/diaphragm inner ring 116, the front platemay include such a hook instead or in addition for engaging a respectivechannel in the diaphragm inner ring/nozzle web structure. Furthermore,while a hard tooth 131 has been illustrated as integrated in the frontplate 154, it is to be understood that in addition or in the alternativeeither the front plate 154 or the back plate 156, or both, could have ahard tooth integrated therewith. Additionally, while only a single hardtooth has been illustrated, it is to be understood that the axialthickness of the respective plate could be adjusted to accommodate avarying number of teeth. Even further, while an example embodiment ofthe seal has been illustrated and described as going directly into thediaphragm (nozzle) inner ring (web), additionally, the new seal assemblycould go directly into a groove in the stator above the bucket tip andcreate a seal there. This could be part of the casing or part of thediaphragm outer ring.

Thus, while the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A seal member for a turbo machine comprising: a brush seal carrier; abrush seal component mounted to said brush seal carrier so that aportion of said brush component projects from said brush seal carrier,and at least one hard tooth seal element integrally formed with saidbrush seal carrier so as to extend in generally parallel relation to atleast a part of said portion of said brush component that projects fromsaid brush seal carrier.
 2. A seal member as in claim 1, wherein saidbrush seal carrier comprises a front plate and a back plate with saidbrush seal component being disposed therebetween, and wherein said frontplate, back plate and brush seal component are integrated by welding. 3.A seal member as in claim 2, wherein said hard tooth seal element isintegrally formed in one piece with said front plate.
 4. A seal memberas in claim 2, wherein at least one of said front plate and back platedefines a hook portion for engaging a corresponding channel of a supportstructure to which the seal member is adapted to be mounted.
 5. A sealassembly for a turbo machine having a rotary assembly rotatable about anaxis and a stationary assembly encircling the rotary assembly, therotary assembly defining outer peripheral surfaces and the stationaryassembly having a portion radially facing the rotary assembly so as tobe in opposed facing relation to an outer peripheral surface thereof,the seal assembly comprising at least a portion of said outer peripheralsurface of the rotary assembly and a plurality of seal elements providedon a seal carrier on said radially facing portion of the stationaryassembly, said plurality of sealing elements including at least one sealelement mounted to said seal carrier and disposed in rubbing contactwith said outer peripheral surface and at least one hard tooth sealelement that is spaced from said outer peripheral surface, and whereinsaid hard tooth seal element is defined integrally in one piece withsaid seal carrier.
 6. A seal assembly as in claim 5, wherein said sealelement in rubbing contact comprises a brush seal component.
 7. A sealassembly as in claim 5, wherein said portion of said outer peripheralsurface of the rotary assembly in rubbing contact with said seal elementcomprises a platform supported radially outward of axially adjacentportions of the rotor.
 8. A seal assembly as in claim 7, furthercomprising at least one air cavity defined below said supportedplatform.
 9. A seal assembly as in claim 6, wherein a single integralhard tooth seal is defined in parallel relation to said brush sealcomponent.
 10. A seal assembly as in claim 5, wherein the turbo machineis a steam turbine.
 11. A seal assembly as in claim 5, wherein said sealcarrier is separately formed from and detachably secured to saidstationary assembly.
 12. A method of providing a seal in a turbomachine, between a rotary member rotatable about an axis and astationary member encircling the rotary member, the rotary member havingan outer circumferential surface; comprising: providing a seal assemblyincluding first and second seal components at a radially inward regionof the stationary member, the first seal component having a portionthereof in rubbing contact with the outer circumferential surface of therotor and the second seal component being integrally formed in one piecewith a carrier of said first seal component and extending in generallyparallel relation to the first seal component but spaced from said outercircumferential surface.
 13. A method as in claim 12, wherein saidcarrier is detachably secured to said stationary member.
 14. A method asin claim 12, wherein said carrier comprises a front plate and a backplate with said first seal component being disposed therebetween, andfurther comprising integrating said front plate, back plate and firstseal component by welding.
 15. A method as in claim 14, wherein saidsecond seal component comprises a hard tooth element integrally formedin one piece with said front plate.
 16. A method as in claim 12, furthercomprising forming a platform on the rotary member for said rubbingcontact with said first seal component.
 17. A method as in claim 16,wherein the platform is fabricated so that a cavity is definedtherebelow.
 18. A method as in claim 17, wherein the platform isfabricated so that the cavity is entirely closed.
 19. A method as inclaim 18, wherein the platform is fabricated so as to contain only air.